Arabidopsis NADK2 (NAD kinase 2) is a chloroplast-localized enzyme involved in NADP synthesis, which acts as the final electron acceptor in the photosynthetic electron transfer chain. The NADK2-deficient mutant (nadk2) was used to analyze the effect of NAD(P)(H) unbalance in the dark-induced leaf senescence. During senescence, WT plants and nadk2 mutants showed a similar reduction in chlorophyll content. NAD(P)(H) quantification showed that the amount of total NAD(P)(H) decreased on the day 7 in WT but on the day 3 in nadk2. The phosphorylation ratio (i.e. NADP(H)/NAD(H)) decreased on day 1 in WT. In contrast, the nadk2 showed lower phosphorylation ratio at 0 day and no change throughout the aging process. Metabolome analysis showed that the metabolic profiles of both WT plants and nadk2 mutants subjected to dark-induced senescence adopted similar patterns as the senescence progressed. However, the changes in individual metabolites in the nadk2 mutants were different from those of the WT during dark-induced senescence.
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http://dx.doi.org/10.1080/15592324.2023.2215618 | DOI Listing |
Plant Signal Behav
December 2023
Graduate School of Science and Engineering, Saitama University, Saitama-city, Saitama, Japan.
Arabidopsis NADK2 (NAD kinase 2) is a chloroplast-localized enzyme involved in NADP synthesis, which acts as the final electron acceptor in the photosynthetic electron transfer chain. The NADK2-deficient mutant (nadk2) was used to analyze the effect of NAD(P)(H) unbalance in the dark-induced leaf senescence. During senescence, WT plants and nadk2 mutants showed a similar reduction in chlorophyll content.
View Article and Find Full Text PDFJ Plant Physiol
April 2023
Graduate School of Science and Engineering, Saitama University, 225 Shimo-Okubo, Sakura-ku, Saitama-city, Saitama, 338-8570, Japan. Electronic address:
Nicotinamide adenine dinucleotides (NAD and NADP) are electron mediators involved in various metabolic pathways. NADP(H) are produced by NAD kinase (NADK) through the phosphorylation of NAD(H). The Arabidopsis NADK3 (AtNADK3) is reported to preferentially phosphorylate NADH to NADPH and is localized in the peroxisome.
View Article and Find Full Text PDFJ Plant Res
January 2023
Graduate School of Science and Engineering, Saitama University, 225 Shimo-Okubo, Sakura-Ku, Saitama-City, Saitama, 338-8570, Japan.
Chloroplast-localized NAD kinase (NADK2) is responsible for the production of NADP, which is an electron acceptor in the linear electron flow of photosynthesis. The Arabidopsis T-DNA-inserted mutant of NADK2 (nadk2) showed delayed growth and pale-green leaves under continuous light conditions. Under short-day conditions (8 h light / 16 h dark), the nadk2 mutant showed more severe growth inhibition.
View Article and Find Full Text PDFHum Mol Genet
November 2022
The Jackson Laboratory, 600 Main St., Bar Harbor, ME 04609, USA.
NADK2 encodes the mitochondrial form of nicotinamide adenine dinucleotide (NAD) kinase, which phosphorylates NAD. Rare recessive mutations in human NADK2 are associated with a syndromic neurological mitochondrial disease that includes metabolic changes, such as hyperlysinemia and 2,4 dienoyl CoA reductase (DECR) deficiency. However, the full pathophysiology resulting from NADK2 deficiency is not known.
View Article and Find Full Text PDFPlant Physiol
August 2022
Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China.
In oxygenic photosynthesis, NADP+ acts as the final acceptor of the photosynthetic electron transport chain and receives electrons via the thylakoid membrane complex photosystem I (PSI) to synthesize NAPDH by the enzyme ferredoxin:NADP+ oxidoreductase. The NADP+/NADPH redox couple is essential for cellular metabolism and redox homeostasis. However, how the homeostasis of these two dinucleotides is integrated into chloroplast biogenesis remains largely unknown.
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